Why Do Your Eyes Turn Red When You Smoke Cannabis?

One of the most prevalent and well-known side effects of using marijuana is red eyes. While harmless, it’s not always desirable for every user. After all, having red eyes is a dead giveaway that you’re high or have recently consumed marijuana.

This article explores the reasons behind why weed makes your eyes red and offers solutions to alleviate this effect.

Why Does Cannabis Cause Red Eyes?

First and foremost, it’s not the smoke itself that causes red eyes. The actual reason is quite fascinating.

Marijuana causes red eyes due to its impact on intraocular eye pressure or the fluid pressure within the eyes.

When you consume tetrahydrocannabinol or THC, your blood pressure decreases. This results in the widening of blood vessels and capillaries, allowing them to carry a greater amount of blood. As a result, less blood returns to the heart in a given moment.

The blood vessels supplying blood to your eyes also dilate after THC consumption, increasing blood flow and lowering the blood pressure in your eyes. This is why medical marijuana is beneficial for glaucoma patients.

However, this increased blood flow in the eyes leads to redness. Since it’s the consumption of THC that causes red eyes and not the smoke itself, you’ll find that your eyes can turn red even with smokeless consumption methods like edibles.

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This is not the only reason for red eyes caused by cannabis, though.

In some rare cases, excessive coughing can burst a blood vessel, resulting in a small red spot appearing on the whites of your eyes.

In this article, we will focus on the most common cause of red eyes – lowered intraocular eye pressure following the consumption of THC.

How Long Do Red Eyes Last?

If your eyes turn red after using cannabis, the redness can last for around 1 to 4 hours. However, in many cases, the redness starts to clear up within an hour or so.

At the end of the day, the duration and intensity of red eyes are not set in stone. Your eyes could be extremely red for hours after one session and completely normal the next.

The most significant factor influencing how red and how long your eyes will stay red is the amount of THC you consume. A general rule of thumb is that the more cannabis you consume and the stronger the effects, the more likely it is that you’ll experience red eyes.

However, this is not a strict rule. Other factors such as age, tolerance/sensitivity to THC, and general health can also determine the extent of redness, if any.

Why Do Some People Not Get Red Eyes?

Not everyone experiences red eyes after using cannabis, and even those who do may not experience the same degree of redness.

For those who don’t get red eyes, there can be various explanations.

Firstly, heavy smokers may develop greater tolerances to THC. In these individuals with high weed tolerance, consuming THC may not lower the intraocular pressure enough to cause red eyes, while still delivering the desired effects.

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The overall health of a user can also affect whether THC causes red eyes. For example, individuals with high or low blood pressure may experience different levels of redness or none at all.

How to Reduce Red Eyes Quickly

Experiencing red eyes after using cannabis is quite common. However, it doesn’t mean you necessarily want your eyes to be red, especially in social situations.

Here are a few methods you can try to quickly reduce red eyes:

1. Use Over-the-Counter Eye Drops for Allergies

Eye drops designed for allergy relief can effectively reduce redness caused by cannabis. These drops contain tetryzoline, which restricts dilated blood vessels and reduces redness. Since THC causes the vessels in your eyes to expand, tetryzoline can counteract the redness without affecting your high.

2. Apply a Cold Compress

Using a cold compress can potentially help alleviate red eyes. Cold compresses are commonly used to reduce eye swelling or pain and can cause blood vessels to constrict in response to low temperatures.

3. Drink Coffee

Caffeine, like tetryzoline found in eye drops, constricts blood vessels when consumed. Grabbing a cup of coffee could help reduce redness in your eyes from smoking weed. However, drinking coffee may also diminish the psychoactive effects of marijuana, so if you want to avoid reducing your high, it’s best to consume caffeine moderately.

4. Eat High-Sodium Foods

Eating snacks high in sodium can temporarily increase your blood pressure. Since marijuana temporarily lowers blood pressure and causes redness, opting for salty snacks like potato chips or popcorn may counteract this process to some extent.

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Can Drinking Water Help?

Many people mistakenly believe that drinking water helps reduce eye redness. Unfortunately, this is not the case. While water may help if you’ve consumed too much cannabis, it won’t alleviate red eyes.

Can You Prevent Red Eyes?

Avoiding red eyes entirely after using marijuana may not be possible for some users.

Regardless of what you do, THC will still lower your blood pressure. However, you can try microdosing or using marijuana strains with lower THC levels to minimize the biological effects and reduce the likelihood of red eyes.


Having red eyes after smoking is one of the most iconic aspects of marijuana use. However, it’s not always a desirable effect, especially if you want to avoid suspicion during a drug test.

The redness of your eyes, if any, depends on various factors such as the type of cannabis product, your tolerance, age, and overall health. It can even vary from day to day.

Fortunately, as discussed in this article, there are several methods you can try to help reduce red eyes after consuming marijuana.

If you found this article helpful, check out some other articles we’ve published:

Disclaimer: The information provided in this article, including any accompanying images or charts, is for educational purposes only. It is not a substitute for professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, always consult with an attorney, physician, or other licensed professional.

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